The closest prior approaches to the assembly of the present invention are the compressed gas filter assemblies of Frantz U.S. Pat. Nos. 4,113,451 and 4,199,331. Both these assemblies have alternately filtering filter units each alternating between filtering and regenerating cycles and contain in the units' housings a particulate desiccant for maintaining a continuous output of filtered and dried gas, effect the alternate filtering and regenerating cycles by timer-controlled solenoid valves and are adapted to interrupt the cycling and force both units to pass gas when the pressure in the line downstream of the unit falls below a predetermined level. However, the housings of those units are separate, do not have common manifolds containing their inlet and outlet valves and require complex external piping connecting each unit's valves in series for ensuring that in a regenerating cycle the inlet and outlet valves close before opening and open after closing of the drain valve and enabling each unit in its filtering cycle to supply regenerating gas to the other unit. It is to an improvement on the assemblies of those Frantz patents that the present invention is particularly directed.